1. Field of the Invention
The present invention relates generally to mining machines utilized in underground mining operations, and, more particularly, to a power supply system for supplying electrical power to individual asynchronous motors one of which supplies torque to drum-cutter and another of the drive motors supplies torque to propel the mining machine along the mine face.
2. Description of the Prior Art
Longwall mining procedures typically utilize an electrically powered drum-cutter mining machine to release coal from a mine wall face. The drum cutter loader mining machine, also sometimes referred to as a shearer loader, includes one or two circular cutting drums supported by an arm at ends of the mining machine.
In the underground mine working operation, it is typical to form in the mine work area two spaced laterals which are passageways extending from a main galley area of the mine. The laterals are typically spaced apart at a distance of several hundred feet, and the laterals are interconnected at their distal ends by a tunnel having a sidewall comprising a longwall mine face. Once the longwall mine face has been created, a longwall conveyor having a rack structure attached thereto is erected along the longwall mine face. The drum-cutter mining machine is then positioned on conveyor proximate to the longwall mine face whereat longwall mining operations may commence. Translation of the mining machine along the mine wall face is achieved by means of a geared connection between the mining machine and the rack structure.
West German Patent Application P 37 16 668.9 discloses a drum-cutter mining machine provided with a winch driven by an electric drive motor arranged at a right angle to the direction of machine travel and provides torque to rotate a drive wheel of the winch. The drive wheel engages a chain or with the teeth of the rack structure to thereby allow translation of the mining machine along the face conveyor. Reduction gearing drivenly interconnects the drive wheel with the motor. The drive motor is designed as three-phase short-circuited rotor supplied with electrical power from a frequency converter, for example, a steplessly adjustable transistor inverter.
West German Patent DE-AS 12 33 356 discloses a drum-cutter mining machine provided with two electric motors, the first of which comprises a drive motor to drive a winch for allowing translation of the mining machine, and the second of which comprises a cutting-drum motor to drive the cutting tool. The two motors receive electrical current from controllable inverters comprised of silicon cells (thysistors) supplied with three-phase alternating current by a contactor in the mine drift. The thyristors coordinated with the drift contactors located in the drift area of the mine allowing the frequency and/or output voltage of the load current supplied to the motors to be steplessly controllable. This control of speed and/or load current thereby allows the motor torque of the motors to be set at any desired value, or altered, steplessly, so that the winch and cutter drum each operate at the most favorable speed. Control lines comprising electrical cables extending to rectifiers connected to a contractor in the mine drift are necessary to allow the operator of the mining machine to control the rectifier and contactor circuits located in drift area of the mine and thereby control the cutting drum speed and speed of travel by the mining machine during mining operations in either direction of travel by the machine. In order to match the speed of travel by the mining machine with the underground mining operations, it is necessary to control the winch motor and the cutting drum motor independently of one another by coal-cutter cables which connect the drift contractor with the cutter drum motor and the winch motor.
If all the equipment required in order to control the speed of both of the motors were to be positioned within the body of the mining machine, an large increase to the dimensional size of the mining machine body would be required to accommodate such equipment. It is important, of course, to minimize the dimensions of the mining machine used in an underground mine.
It is therefore an object of the present invention to provide a space saving construction and arrangement of a drum-cutter mining machine with two independently controllable electric drive motors in a machine body of minimal dimensions.
It is a further object of the present invention to provide a drum-cutter mining machine which includes independently controllable drive motors and cutting drum motors.
It is a still further object of the present invention to provide an improved arrangement of equipment of electrical supply system for a drum-cutter mining machine which includes a rectifier circuit in a mine drift area and controllable inverters on the mining machine.